
message("sub1: CMAKE_SOURCE_DIR: ${CMAKE_SOURCE_DIR}")
message("sub1: CMAKE_BINARY_DIR: ${CMAKE_BINARY_DIR}")
message("sub1: CMAKE_CURRENT_SOURCE_DIR: ${CMAKE_CURRENT_SOURCE_DIR}")
message("sub1: CMAKE_CURRENT_BINARY_DIR: ${CMAKE_CURRENT_BINARY_DIR}")

#只会改变当前scope的值，不会改变parrent scope的值
message("sub1: variable ${variable}")
set(variable world)
message("sub1: variable ${variable}")
